Chapter 3

Chapter 3 big idea

People act effectively by combining memory, environmental cues, constraints, and cultural knowledge

Knowledge in the world

Labels, signs, layout, and reminders; supports first-time use (high discoverability), but can become cluttered or disappear if the environment changes

Knowledge in the head

Learned facts, skills, habits, and conventions; efficient once learned, but requires learning and can be forgotten

Declarative knowledge

Knowing facts and rules (e.g., "the gearshift must be in reverse")

Procedural knowledge

Knowing how: skilled action learned through practice; hard to put into words

Working memory

Limited, fragile memory for the just-present

Long-term memory

Reconstructed memory for past knowledge and experience (not an exact recording)

Natural mapping

A control layout that matches the layout of the objects it controls

Reminder design

A good reminder includes both a signal (draws attention) and a message (what to remember)

Prospective memory

Remembering to perform a planned action at a future time

Transactive memory

A group recalls something together by each person contributing partial knowledge

Norman's three levels of mapping (best to third-best)

1) Controls mounted directly on the item; 2) Controls as close as possible to the item; 3) Controls arranged in the same spatial layout as the items

Penny recognition example

People use coins well without recalling precise visual details; they only need enough to tell coins apart

Saab ignition example

A rule hidden in the head (car must be in reverse to remove the key) fails first-time users because there is no cue in the world

Stove controls example

Poor mapping forces labels and memory; a spatial mapping of controls to burners reduces error

Pilots and air-traffic control example

Critical information is written down or entered into equipment immediately instead of held in memory

Ch. 3 software lessons

Don't make users memorize arbitrary commands; use menus, labels, previews, and persistent state; chunk information; standardize only when better mapping isn't practical

Pitfall: hidden commands depend on prior training

Fix: put key information at the point of use

Pitfall: similar items require unexpected precision

Fix: make differences perceptually obvious

Pitfall: reminders signal but don't carry the message

Fix: pair reminders with content and timing

Pitfall: cultural assumptions treated as universal

Fix: test mappings across cultures and contexts

Best memory aid (Ch. 3 takeaway)

Making memory unnecessary

Review: How can people perform precisely with imprecise memory?

The world can provide cues that work together with knowledge in the head

Review: Benefit of natural mapping in a control layout

It reduces memory load and errors by matching controls to what they affect

Review: Which description matches procedural knowledge?

Knowing how to perform a skilled action through practice

Review: What should a good reminder include?

Both a signal and a message

Review: What does Ch. 3 say about mappings that feel "natural"?

Culture can change what feels natural

HW A1: Shopper uses familiar routines + on-screen instructions at self-checkout

Remembered knowledge and visible information work together to guide action

HW A2: Stating "Borrowed equipment must be returned before 5 p.m."

Declarative knowledge: knowledge of a fact or rule

HW A3: Types fluently without looking but can't describe finger movements

Practice has developed procedural knowledge that is difficult to verbalize

HW A4: Can't draw a coin but uses it correctly

They need enough information to distinguish the coin from relevant alternatives

HW A5: Connector fits its socket only one way

It reduces the physically possible actions the user must choose among

HW A6: Novice prefers labeled menus, expert prefers learned commands

Visible information reduces initial learning but can take time to find and interpret

HW A7: Registration code disappears after an interruption; best fix

Keep the code visible next to the field until entry is complete

HW A8: Runner remembers digits as race times

The digits become meaningful chunks linked to existing knowledge

HW A9: Recalling an old event differently after a new interpretation

Remembering reconstructs and interprets stored information rather than replaying an exact record

HW A10: Arbitrary task codes replaced by goal-based groups

The organization connects new material to meaningful relationships users can understand

HW A11: How to judge a simplified model

By whether it supports appropriate behavior in the situation for which it is used

HW A12: Technician hears settings in sequence (pilot approach)

Enter each setting into the relevant control as it is heard, keeping the values visible

HW A13: Remembering to return a camera tomorrow

Prospective memory

HW A14: Alarm sounds but student forgets its purpose; missing component

The message identifying what needs to be remembered

HW A15: Instructions left in a closed drawer; best fix

Arrange for the instructions to appear when and where the student must prepare to leave

HW A16: Friends recover a restaurant name by combining clues

Transactive memory

HW A17: Team relies on a shared digital reference that may be wrong or unavailable

The aid can improve performance, but accuracy and continued access still matter

HW A18: Four lights in a 2x2 square, switches in a vertical list; best redesign

Arrange the switches in a 2x2 square matching the lights from the user's viewpoint

HW A19: Strongest mapping in Norman's three-level ranking

Mount each control directly on the item it operates

HW A20: Users disagree on natural scroll direction

Their different metaphors (moving text vs. moving window) create different, internally coherent expectations

HW A21 fill-in: Facts and rules a person can state are ____ knowledge

declarative

HW A22 fill-in: Dividing a long digit string into meaningful groups creates memory ____

chunks

HW A23 fill-in: A reminder needs a ____ to draw attention plus a message

signal

HW A24 fill-in: Remembering to perform a planned action later is ____ memory

prospective

HW A25 fill-in: The relationship between controls and the objects they affect

mapping

Laws of UX Part 1: the five laws

Jakob's Law, Fitts's Law, Hick's Law, Miller's Law, Postel's Law

Jakob's Law

(Jakob Nielsen) Users spend most of their time on other sites and products, so they expect yours to work like the ones they already know; use standards and conventions where available

Jakob's Law key takeaway

Innovation should not come at the cost of usability; familiarity reduces learning time and cognitive effort

Jakob's Law examples

Cart icon in the upper right; bottom navigation bars on mobile; underlined/colored text for links; magnifying glass for search

Does Jakob's Law mean you can't innovate?

No; use branding and unique features to stand out, but roll out major changes carefully and gradually (good: Gmail, YouTube; bad: Windows 8)

Fitts's Law

(Paul Fitts, 1954) The time required to reach a target depends on its size and distance; larger, closer targets are faster and easier to select

Fitts's Law formula

ID = log2(2D / W), where ID = index of difficulty, D = distance to target, W = width of target

Fitts's Law design implications

Make frequent buttons larger; place controls near where users already focus; reduce pointer/finger movement; space targets apart; size touch targets for fingers

Fitts's Law examples

Large Submit/Add to Cart button (Submit near the last field); floating action button within thumb reach; controls at screen edges (edges stop the pointer); tiny "X" close buttons are hard to hit

Google Material Design minimum touch target

48 x 48 dp (density-independent pixels)

Hick's Law

(Hick & Hyman, 1950s) The time to make a decision increases as the number and complexity of choices increase

Hick's Law goal

Not always fewer choices, but clearer, better-organized choices; grouping is your friend

Hick's Law design implications

Limit choices at critical moments; group related options; use progressive disclosure (reveal complexity only when needed); highlight recommended actions; remove rarely used options

Hick's Law examples

Streaming content grouped by genre; forms asking essential questions first; a highlighted "Most Popular" pricing plan; a simple nav menu instead of dozens of equal links

Miller's Law

(George A. Miller, 1956) The average person can keep about 7 ± 2 items (chunks) in working memory

Important caveat about Miller's Law

Working memory may be even more limited, so chunking matters more than the exact number; don't treat 7 as a magic number

Miller's Law design implications

Chunk content; use headings, sections, and lists; don't make users remember info between screens; avoid unnecessary tasks; support recognition over recall (show options, hints, visible instructions)

Miller's Law examples

Chunked phone numbers; multi-step checkout (one task at a time); grouped navigation categories; password requirements shown on screen

Postel's Law

(Jon Postel, TCP; a.k.a. the robustness principle) Be conservative in what you do, be liberal in what you accept from others

Postel's Law design implications

Accept input variations (except passwords); fail gracefully with meaningful feedback; maximize interoperability and backward compatibility; ensure predictable, consistent output

Postel's Law caveat #1

Be mindful of maintainability: overly permissive input rules complicate code and documentation

Postel's Law caveat #2

Be accepting, but not too accepting: unsanitized input can open the system to attacks (e.g., SQL injection, XKCD "Bobby Tables")

HW B1: Jakob's Law suggests users…

Prefer interfaces that work similarly to those they already know

HW B2: Shopping site keeps navigation like other popular e-commerce sites

Jakob's Law

HW B3: Fitts's Law is primarily concerned with…

The time required to reach a target based on size and distance

HW B4: Easiest target to click under Fitts's Law

A large button close to the cursor

HW B5: Change that best improves usability per Fitts's Law

Making a primary action button larger

HW B6: Strategy that best reflects Miller's Law

Organizing information into smaller, meaningful chunks

HW B7: Design choice that best aligns with Jakob's Law

Using familiar menu patterns and predictable layout conventions

HW B8: Why a highly original interface causes problems (Jakob's Law)

It increases cognitive load by forcing users to learn new patterns

HW B9: Form requires remembering a long list of requirements across steps

Miller's Law

HW B10: Hick's Law states that…

Decision time increases with the number and complexity of choices

HW B11: Small, hard-to-reach button for a frequent action violates…

Fitts's Law

HW B12: Scenario that best illustrates Hick's Law

A user overwhelmed by 40 filter options in an online store

HW B13: Streaming service cuts homepage categories from 18 to 6

Hick's Law

HW B14: Postel's Law advises designers to…

Accept varied user input gracefully while being consistent in output

HW B15: Date field accepts 10/12/26, October 12 2026, 2026-10-12 and formats consistently

Postel's Law

HW B16: Situation that best reflects Postel's Law

A search bar returns useful results despite spelling variations

HW B17: System rejects valid input that doesn't match one exact format; fails to apply…

Postel's Law

HW B18: Breaking a long onboarding flow into short sections to reduce overload

Miller's Law

HW B19: Miller's Law is most closely related to…

The limits of working memory

HW B20: Decision most likely to increase decision time (Hick's Law)

Presenting many equally weighted choices at once

HW B21 fill-in: Users prefer your site to work like sites they already ____

know

HW B22 fill-in: Larger, closer targets are faster and easier to ____ (Fitts's Law)

select (click / reach)

HW B23 fill-in: Miller's Law is addressed by ____ (grouping into meaningful units)

chunking

HW B24 fill-in: More, more complex choices increase the time to make a ____

decision

HW B25 fill-in: Postel's Law: be flexible in accepting user ____

input